Refrigerating apparatus



Dec. 29, 1936. D. E. MACCABEE I 3 5 REFRIGERATING' APPARATUS a FiledMarch so, 1929 III III 5 0m 2? 4 ya 5M 5!!!! U G Q 37 37 30 27 "L": I III.- Q Q 7////./ ///////,1. 1% 7////////. AW/////A 3mm Patented Dec. 29,1936 PATENT OFFICE rmrmenm'rme APPARATUS David E. Maccabee, Dayton,Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation ofDelaware Application March 30, 1929, Serial No. 351,362 '4 Claims. (01.62-8) This invention relates to refrigerating apparatus and particularlyto arrangements for controlling the circulation of refrigerant in suchapparatus.

One of the objects of the invention is to provide an improved controlsystem particularly adapted to multiple installations whichautomatically prevents the circulation of refrigerant in such unit orunits of the system as do not need refrigeration.

Another object of the invention is to provide an improved refrigeratingsystem in which one condensing element supplies a number of evaporatingelements with refrigerant and automatically maintains each of themwithin predetermined temperature limits independent of the remainingelements.

More specifically it is an object to provide such a system in which theoutlet of one or more. of the evaporators is positively closed whenthere is no refrigerating demand upon such evaporator,

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein a preferred form of the present invention is clearlyshown.

In the drawing:

Fig. 1 is a diagrammatic representation of one form of refrigeratingsystem embodying my invention, and

Fig. 2 is a sectional view showing the construction of a control valveof the system.

It has previously been proposed to provide a number of evaporators whichare supplied with refrigerant from a common condensing element and tooperate the-system so as to maintain the different evaporators atdifferent temperatures. In the previously known systems of thischaracter the different evaporators are not entirely independent of eachother and the condensing element does not circulate refrigerant throughthe various evaporators in accordance with the refrigerating demand uponeach. The difliculties experienced have been the more pronounced incases in which it is sought to maintain widely different temperatures.My invention is concerned with'providing a simple, economical andreliable system which will satisfactorily maintain widely differenttemperatures and in which the various refrigerating elements areoperated independently of one another.

Referring to the drawing, l0 designates in general a condensing elementfor withdrawing gaseous refrigerant from a vapor conduit ll,

liquefying the refrigerant and delivering it to a liquid supply conduitl2. The condensing element may be of any desired type, for example itmay include the usual motor I4, compressor l5 and condenser IS, themotor beingactuated in response to the pressure within the conduit II bymeans of an automatic switch l8 which connects the motor to power mainsl9. Evaporators 20 and 2| are connected in parallel between the liquidsupply conduit and the vapor exhaust conduit II for cooling compartments20a and 2la. The evaporators are connected to the conduit H by means ofindependent outlet conduits 23 and 24. Preferably each of theevaporators is of the flooded type and includes a reservoir for liquidrefrigerant which is kept at a constant level therein by means of afloat valve, not shown herein but fully disclosed in the patent toOsborn 1,556,708, October 13, 1925. Since the evaporators are of theflooded type, the pressure of the refrigerant in each will correspond to-its temperature. Assuming that the evaporator 2| is to be kept at thehigher temperature and pressure, I place in the outlet of thisevaporator a shut-off valve 26, the construction of which is illustratedin Fig. 2 and which automatically closes when the evaporator 2! hasreached a predetermined low pressure.

A valve casing 30 having an inlet 3| and an outlet 32 is connected inthe conduit 24. Within the casing is a valve seat 2'! and a valve proper25 which is either moved to the left to permit unrestrictedcommunication between the inlet and outlet, or else is moved to theright against the seatto positively close the outlet, by means about tobe described. The casing 30 is provided with a boss 34 to which issealed the open end of a flexible metal bellows 35, the other. end ofwhich .is closed. in any suitable manner. Preferably the bellows isclosed at its upper end by a cap 36 soldered to the bellows and itsother end is soldered to an end cap 31 secured to the boss 34 in anysuitable manner, the cap 37 having an opening 38 to providecommunication between the bellows and the casin 30. I

The end cap 36 0f the bellows is connected to the valve by a link 39,the bellows forming a motor for operating the valve in response to thepressure within the casing 30. When the pressure is high the bellows.expands to open the valve and when the pressure is low the bellowscontracts to close the valve.

In order that the valve may be suddenly opened at. a predetermined highpressure and remain open until suddenly closed by a predetermined lowpressure I provide a snap acting mechanism for controlling the movementof the valve under the influence of the pressure in a casing. This isexemplified in Fig. 2 as a rod 40 secured to the end cap 36 of thebellows and reciprocable in a guideway formed by openings 4| and 42 instationary posts 43 and 44 suitably secured to a base 45 upon which thevalve casing may also be supported by being attached to a bracket 46.The portion of each post 43 and 44 below the openings 4| and 42 ishollow and contains a spring-loaded plunger or detent including a piston41, a ball 48, a spring 49 and a spring abutment 50. The hollow. portionof the post is slotted as indicated at 5|, the spring abutmentprojecting through the slots to the outside of the post and resting upona nut 52 by which the tension of the spring can ,be adjusted. The rod 40is provided with detent receiving means in the form of a pair of notches54 and 55 which are adapted to receive the detents in posts 43 and 44respectively. The notches 54 and 55 are so spaced that when the notch 55receives the detent in the post 44 the valve is held in a fully openedposition and when the notch 54 receives the detent in the post 43 thevalve is held closed. The posts may be suitably braced or held togetherat their upper ends by means of a bar 60 secured to each post by screw6|.

The operation of the valve is as follows.

With the parts in the position shown in Fig. 2, assume that the pressurein the casing 30 is diminishing. The bellows attempts to contract andclose the valve, but is prevented from moving the valve by the force ofthe spring detent in the notch 55. Eventually the pressure reaches sucha low value that the force of the bellows overcomes the force of thedetent, and the rod 40 slides suddenly to the right, suddenly andpositively closing the valve. As this occurs the notch 54 registers withthe detent in the post 43 and retains the rod in the position in whichthe valve is closed. Upon a subsequent increase in pressure, the bellowstends to expand, but the notch 54 prevents movement of the rod and ofthe valve until a definite high pressure is reached which overcomes theforce of the spring detent in tube 43. When this occurs the rod issuddenly moved to the left and the valve suddenly opened.

The springs in posts 43 and 44 may be independently adjusted todetermine the pressures at which the valve opens or closes respectively.Thus any desired closing pressure can be selected which is independentof the opening pressure and vice versa.

I have found that at certain pressure settings difficulty may beexperienced in getting the rod to suddenly jump from the position inwhich the notch 55 is engaged to the position in which the notch 54 isengaged or vice versa. This may result in leaving the rod unlocked andrender the valve subject to movement in response to gradual or smallchanges of pressure. To overcome this the rod is given a large inertia,as by attaching a weight 10 so that when the rod has been placed inmotion a suflicient amount to release the detent in either notch, themomentum will snap it to the other position, positively flexing thebellows to insure locking the rod in the other notch. In order tofacilitate the attainment of this momentum, particularly on opening thevalve, the link 39 is secured to the cap 36 thru a lost motionconnection II. It has also been found desirable to provide a lightspring 12 for positively holding the valve tight on its seat to preventleakage due to wear in the lost motion connection or play between thedetents and notches.

In operating with closing pressures in the neighborhood of atmospheric,the pressure of the atmosphere on the bellows may not be sufficient toclose the valve. In such cases the spring 13, under compression betweenthe post 43 and a pin in the rod 40, assists in the closing of thevalve, the tension of the spring detent in post 44 being regulatedaccordingly.

The automatic switch i8 is set to operate at low pressures correspondingto the temperatures to be maintained in the evaporator 20. Whenever thetemperature of 20 is above the maximum permissible value, the pressureof the refrigerant will actuate the switch l8 to operate the condensingelement. Under these conditions refrigerant will not be evaporated inthe evaporator 2| unless the valve 26 is open. Whenever the valve isopen, the condensing element will reduce the pressure and temperature ofthe evaporator 2| to its lowest permissible value (which is above thesetting of the switch l8) at which point the valve will close to preventfurther refrigeration in 2|. If the evaporator 20 should at any time bewithin its normal temperature limits, and the condensing elementconsequently be idle, and the evaporator 2| should become too warm, thepressure in 2| will open the valve and allow the high pressure to becommunicated to the conduit II and switch l8. Since this high pressureis above the value which closes the switch, the switch will be operatedimmediately to start the condensing element. Refrigerant will then bewithdrawn from both evaporators until both have reached their minimumpermissible temperature. If the evaporator 2i reaches its minimumtemperature first, the valve 26 will close to prevent furtherrefrigeration, and the condensing element will continue to refrigeratethe evaporator 20. Ii, however, the evaporator 20 should reach itsminimum temperature first, the valve will remain open, and the pressureof the refrigerant evaporated in 2! will keep the switch open. However,since each evaporator contains a relatively large quantity of liquidrefrigerant, whose pressure corresponds to its temperature, the rates ofevaporation of the liquid will correspond with the pressures. Hencerefrigerant will be evaporated rapidly in 2! and quickly reduce itstemperature, whereas refrigerant will be evaporated but slowly in 20,and thus its temperature will not be reduced to a value appreciablybelow its normal minimum value.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. A refrigerating apparatus including a pinrality of evaporators, meansfor supplying liquid refrigerant to and for withdrawing gaseousrefrigerant from the evaporators, and a mechanically operatedtwo-temperature snap acting valve responsive to a. predetermined highpressure within one of said evaporators for abruptly opening thewithdrawing means for said one evaporator and responsive to apredetermined low pressure within said one evaporator for abruptlyclosing the withdrawing means for said one evaporator, said valve havinga relatively heavy weight for providing ample inertia to carry the valveabruptly from one position to the other, said valve including adjustingmeans for independently varying said predetermined high pressure andsaid predetermined low pressure at which said valve opens and closes.

2. A mechanically operated two-temperature snap acting valve including avalve case having an inlet portion and an outletportion, a valvefor'controlling the flow of fluid from said inlet portion to said outletportion, a flexible wall in communication with said inlet portion foropening and closing said valve, means for controlling the valve to causeit to open abruptly when a. predetermined high pressure is reached andto cause it to close abruptly when a predetermined low pressure isreached, said last mentioned means including a weight for providinginertia to carry the valve from one extreme position to the otherextreme position, and adjusting means for independently varying saidpredetermined high pressure and said predetermined low pressure at whichsaid valve opens and closes.

3. A mechanically operated two-temperature snap acting valve including aT-shaped valve casing having an inlet portion in one leg and an outletportion in another leg, a flapper type valve located at the entrance ofthe outlet leg for controlling'the flow of fluid from the inlet leg tothe outlet leg, a flexible bellows located at the end of the legopposite the outlet leg, a connecting member connecting said valve andthe movable portion of the bellows, a horizontal rod connecting to themovable portion of the bellows, said horizontal rod having a pluralityof notches therein, a plurality of ball detent meansvadapted toyieldingly engage the notches in the horizontal rod for causing said rodto move with a snap action from one extreme position to another, saidball detent means being independently adjustable and the weight mountedupon said horizontal rod for providing inertia to aid in the abruptmovement from one position to the other, said horizontal rod providing asnap acting opening and closing the flapper valve.

4. A mechanically operated two-temperature snap acting valve including avalve case having an inlet portion and an outlet portion, a valve forcontrolling the flow of fluid from saidinlet portion to said outletportion, pressure operated means for opening and closing said valve,means for controlling the valve to cause it -to open abruptly when apredetermined high pressure is reached and to cause it to close abruptlywhen a predetermined low pressure is reached, said last mentioned meansincluding a weight for

